Magnetic compass



Oct. 31, 1944. A. A. STUART, JR

MAGNETIC COMPASS Original Filed May 21, 1940 3 Sheets-Sheet 1 INVENTOR.g/f/"ed AfZuarlh/P.

J ATTORNEY.

Oct. 31, 1944. A. A. STUART, JR

MAGNETIC COMPASS Original Filed May 21, 1940 3 Sheets-Sheet 2 h/n mm.

INVENTOR. A/f'red A. Siuar III,"

M m I BY jzyyzw ATTORNEY.

Oct. 31, 1944. A. A. STUART, JR 2,361,433

MAGNETIC COMPASS Original Filed May 21, 1940 3 Sheets-Sheet 3 FREQ.

nouns/a I -INVENT0R. Q A wed A. 3mm, Jr.

ATTORNEY.

Patented Oct. 31, 1944 MAGNETIC COMPASS Alfred A. Stuart, In, HasbrouckHelglits, N. 1..

assignor to Bendk Aviation Corporation, Bendix. N. J., a corporation ofDelaware Substituted for abandoned application Serial No 336,444, May21, 1940. This application October 31, 1942, Serial No. 464,095

12 Claims.

The present invention relates to magnetic compasses, and moreparticularly to the so-called earth inductor type of compass, and is acontinuation of application Serial No. 336,444, filed May 21, 1940,entitled Magnetic compass, which is, in turn, a continuation in part ofapplication Serial No. 248,344, filed December 29, 1938, now Patent No.2,240,680, dated May 6, 1941, entitled Earth inductor compass."

Compasses used in navigation, and particularly in navigation ofaircraft, have several disadvantages, chief among which are theirinsensitivity and their undependability during pitch and roll and underthe eflects of accelerations usually encountered on shipboard and inaircraft, and the fact that most earth inductor compasses of the priorart type required the rotation of the earth inductor element forgenerating the required voltage or for follow-up purposes.

The present invention has for one of its objects the provision of anovel structure for overcoming the foregoing and other deficiencies inmagnetic compasses oi the prior art, especially in prior earth inductorcompasses, as will appear more fully hereinafter.

Another object of the present invention is the provision of an improvedmagnetic compass of the earth inductor type in which the earth inductorelement is relatively stationary and has no rotatable or moving partsand is supported on the ship or aircraft in a fixed reference plane by astabilizing yroscope, as distinguished from the earth inductor compassdisclosed in the aforesaid Patent No. 2,240,680 in which the earthinductor includes a rotatable element requiring an electric motor torotate it in order to generate the required electromotlve force fromtheearths magnetic field, thereby making it difllcult to employ astabilizing gyroscope to maintain the inductor in a ilxed, referenceplane.

A further object is toprovide an improved magnetic compass of the earthinductor type disclosed in the aforesaid Patent No. 2,240,680, but inwhich the only rotating parts are in the remote indicator, therebyeliminating the necessity of using an electric motor or other primemover to rotate the earth inductor or any part thereof and making itpossible to readily stabilize the inductor in a fixed reference plane bymeans of a stabilizing gyroscope or gyro-vertical.

Still another object is to provide a novel and improved magneticcompass, the indications of which may be amplified by a torqueamplifier. and also to provide a magnetic repeating device which willrepeat, with amplified torque, the movement of a magnetic needle orother magnetic element.

The foregoing and other objects and advantages of the invention willappear more fully hereinafter from a consideration of the detaileddescription which follows, taken together with the accompanying drawingswherein two embodiments of the invention are illustrated by way ofexample. It is to be expressly understood, however, that the drawingsare for illustration purposes only, and are not to be construed asdefining the limits of the invention, reference bein had for thispurpose to the appended claims.

In the drawings, wherein like reference numerals refer to like parts inthe three embodiments:

Fig. l is a, partly schematic representation of a magnetic compass ofthe present invention;

Fig. 2 is a showing of an essential part of the present invention whichmay be substituted in i Fig. 3 is a showing, partly schematic, of theearth inductor compass stabilized in a horizontal plane by a gyroscope;

Fig. 4 is a schematic illustration of the compass shown in Fig. 1 with aslight change in the circuit thereof.

Briefly, the present invention, instead of having a rotatable earthinductor as in Patent No. 2,240,680, includes a novel pick-up device ofmaterial having high permeability and low retentivity, which isrelatively stationary and which has a portion periodically magneticallysaturated and unsaturated, and another portion having windings connectedin multipolar relation, in which are induced voltages. the relativevalues of which are representative of the angular relation between aselected axis of symmetry of the pickup device and the direction of theearth's magnetic field. These voltages are conducted to a remotereceiving device which may be an Autosyn, in the rotor of which areinduced voltages similar to those induced in the windings of therelatively stationary pick-up device. An indicating pointer connected tothe rotor will, therefore, indicate the direction of the earths magneticfield, or the angular displacement of the pick-up device in the earth'smagnetic field with the craft on which it is mounted. By means of anampliher, the torque of the rotor may be increased to any desired value.

Having particular reference to Fig. 1, l0 designates a relativelystationary and non-rotatable magnetic pick-up device of highly permeablematerial, such as "Permalloy or Mumetal," having legs ll, 12 and I3,symmetrically disposed 120 degrees apart and converging upon the centralring portion or stationary armature I4, 01 the same material. The legsll, I2 and I3 have windings I5, I8 and I1, respectively, wound thereon,and central portion I4 has an exciting winding I8 which may be split upas shown, into three equal portions for the purposes of symmetry.Winding I8 is connected through leads I9 and 20 to a source ofalternating current 2i. Winding s IE, it and I1 have their inner endsconnected to ground, and their outer ends 22, 23 and 24, respectively,are connected to coils 25, 26 and 21, respectively, which are woundabout the poles of the stator 28, of a conventional autosyn motor 29.Rotor 30 of autosyn 28 carries a coil 3i, which is connected throughleads 3! and 33 to the input of vacuum tube amplifier 34. The output ofamplifier 34 is connected through leads 35 and 35 to one phase 31 of atwo-phase induction motor 38. The other phase 39 is energized fromsource 2i through a frequency doubler 40 by way of conductors 4i and 42of any conventional electrical coupling arrangement, such as condenser43 and resistor 44. A suitable frequency doubler 40 may be of anyconventional type; for example, it may be patterned after the frequencydoubler shown and described on pages 706 and 707 of "Principles of RadioCommunication by Morecroft, 2nd edition.

Rotor 45 of motor 38 is geared to rotor 30 through any suitable train 46connected to shaft 41, which has a pointer 48 rotatable therewith forindicating direction upon the compass card of azimuth scale 49. Thecircuit including amplifier 34, induction motor 38, gear train 46, etc.acts to amplify the torque available in rotor 30 and coil 3i, and willbe described later.

Assuming that the relatively stationary earth inductor I is disposed inthe earths magnetic field in a horizontal plane and leg ll parallel withnorth and south, as shown in Fig. 1, with no exciting current in windingI8, the earths field will thread through leg II and equally through legsI2 and I3, through armature I4. As long as the flux in legs i I, I2 andI3 is in a steady state, no voltage will be induced in windings I5, iiiand I1. However, if sufllcient excitation current is suplied to windingill by source II to periodically saturate armature i4, then the earthsflux will leave legs H, I2 and 13 at a rate depending upon the frequencyof source 2i, and a voltage will be induced in each of windings I5, i6and I1, setting up therein, and in coils 25, 26 and 21, an alternatingcurrent. windings I5, I6 and I1 are so situated on legs II, I2 and I3,respectively, that no voltages are induced therein due to the saturationof armature i4. The magnetic field caused by saturation of armature I4flows only through portion l4 and does not enter legs ii, I! and I3.However, in saturating central armature portion I4, the reluctance ofthe path taken by the earth's field in legs II, I2 and I3, prior tosaturation, will become exceedingly high, forcing the earth's field toleave armature l4 and legs II, 12 and I3, and flow through a path oflower reluctance in the air.

While the torque amplifier described above is of decided advantage forcertain uses of the compass of the present invention, there is shown inFig. 4 a circuit which does not employ a torque amplifier, but which isotherwise identical to the circuit shown in Fig. 1. The leads 32 and 33of coil iii are connected directly to the output of frequency doubler40. The currents in coils 25, 26 and 21 will set up a resultant magneticfield accuse in the rotor gap of "Autosyn" 23, and the current in coil3i due to frequency doubler 40 will let up a field so that rotor 38 willb forced to rotate until the field of coil ii is aligned with theresultant field of coils II, 34 and 31. This position will be that atwhich the maximum number of lines or force are passing through coil II.This condition is unique and will take place at only one position of thecoil II !or a given position of the magnetic pick-up device Iii, due tothe phase relation existing between the voltage of frequency doubler 40and the voltage induced in windings I5, I8 and I1 by source 2|. Thus,pointer 48 carried by rotor 30 on shaft 41 will indicate the trueangular disposition of pick-up device Ili with respect to the earth'smagnetic field.

When the compass of the present invention is used to indicate extremelyweak fields, such as the earth's magnetic field, the use of the torqueamplifier above described is desired, as extremely low torques resultingfrom current in coil 3i, acting in conjunction with the magnetic fieldresulting from the flow of currents in coils 25, 26 and 21, may beinsufilcient to overcome the iristion of the bearings and slip-ringsattached to rotor 30. The current in coil II is amplified in the vacuumtube amplifier 34 and its output may be of any desired power ratingwithout causing harmful reaction on coil 3i. It is a well-knowncharacteristic of vacuum tubes that the output has no substantialreactive effect upon the in put. Therefore, unless coil 3| is in a nullposition, phase 31 will be energized, thereby causing rotor 45 to turngear train 46, shaft 41, and along with the shaft, rotor member 30,until this latter member again reaches a null position, at which timephase 31 is de-energized and rotation of rotor 45 thereby stopped.

The winding 39 of one phase of rotor 38 is continuously energized fromsource 2| and through frequency doubler 40. No self-rotation of rotor 45is possible while the winding of only one phase is energized, thuspointer 43 will not be rotated until there is current in coil 3i whichis amplified in amplifier 34 for energizing phase 31, and this conditionis fulfilled only when pick-up device I0 is being rotated in the earthsmagnetic field. The current flowing in coil 3i and phase winding 31 willalways be in the correct phase with respect to that in phase winding 33to cause rotation in the correct direction. Thus, degree ambiguity iseliminated. A torque amplifier, similar to that here disclosed, isdisclosed in the aforesaid application Serial No. 248,344, filedDecember 29, 1938, now Patent No. 2,240,680, and assigned to the sameassignee as the present invention.

Those versed in the art will readily comprehend that upon angulardisplacement of the pick-up device I0 clockwise with respect to themagnetic field by the angle 0, the voltages induced in each of the legsII, I2, and I8 will be changed to the value N cos 0, where N representsthe value of voltage induced when the inductor or pick-up device III isdisposed as shown in Fig. l, and where a is the angle through whichdevice Ill is rotated to its new position; likewise, ii device II] isrotated clockwise through the angle 0, rotor 30 is also rotated throughthe same angle 0, and pointer 48 will indicate angle 0. Thus, for eachangle of displacement of pick-up device IIi in the earth's field,pointer 48 will move through the same angle of rotation. This relationholds true regardless of the angle or the direction of displacement ofpick-up device Ill.

A slightly different earth inductor or pick-up member 56, as shown inFig. 2, may be substituted for the pick-up member Ill in Fig. l, bymerely superimposing Fig. 2 upon the circuit of Fig. 1, so that lines Aand B coincide with Lines A and B, respectively, of Fig. 1. Then theends 22, 23 and 24 of windings I5, l8 and H will be replaced by ends22', 23' and 24' of windings l, l8 and I1, respectively, and leads I9and 20' of exciting winding l8 will be substituted for the leads l9 and20 of exciting winding l8.

With Fig. l modified in this respect, the operation of the completecircuit is identical to the operation of the circuit above describedwith respect to Fig. 1. However, leg members ll, l2 and I3 are connecteddirectly together without the use of a ring, such as II in Fig. 1. Whencurrent from source 2| flows through winding l8, it will saturate eachof the legs l|, l2 and I3 in the central armature area within the circledesignated I4 and no saturating flux will flow through that portion ofthe legs about which are wound coils l5, l6 and I1. It has proved to bean advantage in production to form the pick-up member as represented by5|! in Fig. 2, rather than as shown at II) in Fig. l, but it should beborne in mind that the operation of both members is essentiallyidentical.

Although it is intended to use the circuit oi Fig. l as an earthinductor compass, it may have other possible uses. However, when it isdesired to use the device of the present invention as an earth inductorcompass, it is essential to its faithful operation that the earthinductor or pick-up member in (or pick-up member 50, if this form ispreferred) be maintained in a horizontal plane. To this end it isproposed to mount pick-up member Ill as shown in Fig. 3, upon agyroscope 5|, which is stabilized in any conventional manner about itsvertical axis. Since diflerent means of stabilization of gyroscopesabout the vertical axis are well-known, no description thereof will begiven at this time. However, upon gyroscope casing 52, there are mountedupright members 53 to which is attached a horizontal plate of insulatingmaterial 54, which carries pick-up device Ill secured thereto by anysuitable means. The ends of windings 22, 23 and 24 are connected to thepoles of stator member 28 in the same manner as shown in Fig. 1, andleads l9 and 2|) are also connected to source of alternating current 2|in the manner shown in Fig. 1. Since the circuit of Fig. 3 is identicalto the circuit of Fig. 1, no further explanation thereof is feltnecessary.

It will be readily understood that regardless of pitch, roll or otheraccelerations of a ship or aircraft, gyroscope 5| will be maintainedstable about the true vertical and thus, earth inductor or pick-updevice l0 will be maintained horizontal, and magnetic errors, resultingin false indications of pointer 48, which would appear withoutstabilization of pick-up device III, are thereby absent from the system.

It has been stated above that upon saturation of the central ringportion l4, magnetic flux, which otherwise threads through legs H, H andH, leaves due to the great increase in reluctance which results from thesaturation of ring ll. It is elementary that when flux leaves apermeable member, such as legs l2 and I3, an alternating current isinduced in windings, such as l5, l6 and I1, inductively associatedtherewith. When the current from source 2| falls below its saturatingvalue, which happens twice u during each exciting cycle, the earth'sfield will again thread through legs II, l2 and I3 and induce anotherhalf cycle of alternating current each time in windings l5, I8 and ll.It will be apparent that with a given value of the horizontal componentof the magnetic field, the voltage induced in windings l5, l6 and i1will vary with the frequency of alternation of source 2|.

The voltage induced in these windings also depends upon the saturationcharacteristics of the material used for central ring portion H. Inorder to simplify the explanation of the invention above given, it hasbeen stated that the earth inductor or pick-up device I0 is made of ahigh permeable material, such as Permalloy or Mumetal. A highpermeability is not necessary for the successful operation of thisdevice, and many of the common paramagnetic materials such as siliconsteel and soft iron can be successfully used. However, it has been foundthat the knees of the saturation curves for "Mumetal" and "Permalloyhave an exceedingly sharp bend as contrasted with the gradual, smoothcurves of other magnetic materials. By the use of a material having asharp knee to its saturation curve, a much higher voltage can beinduced, since the saturation with the same exciting voltage and currentwill take place in a much shorter interval. Since the voltage induced inwindings l5, l6 and H will depend to a great extent upon the rate atwhich the earths flux is expelled from legs l2 and HI, it will bereadily apparent that a decided advantage is obtained by the use oithese metals having a sharp bend on their saturation curves.

Instead of an alternating source of exciting current, there may besubstituted for 2|, a source of intermittent or pulsating directcurrent. If this latter source is used, a frequency doubler becomesunnecessary since the frequency in the output of windings I5, l6 and I1will be the same as the frequency of interruption of the direct currentsource substituted for alternatin source 2|. It has been found also thata frequency doubier can be eliminated when a source of alternatingcurrent, such as 2|, is used in conjunction with a direct current biasof a value such that with the bias alone, armature portion I4 issaturated; then on every other half cycle 0! alternating current fromsource 2|, the bias will be overcome by the alternating current and thefrequency in the output of windings l5, l6 and i1 will equal thefrequency of source 2|. The latter arrangement has proven to bebeneficial where it is desired to work at extremely high frequencies ofalternation, since the hysteresis loss is cut down and therefore, moreoutput may be obtained from the windings l5, l6 and ll of pick-up deviceIll.

The earth induction or pick-up devices shown at Ill and 5|] have threelegs, but the use of any desired number of legs, either separate orintegral, such as four, is comprehended within the limits of the presentinvention. If four legs are used, the angular separation may be degrees,and the legs may be formed integrally or of two or four pieces ofmaterial arranged to form a cross.

While only two embodiments of the present invention have been shown inthe drawings, it is to be understood that various changes may be madewithout departing from the scope of the present invention. For thisreason, it is intended not to limit the invention by the descriptionherein given as an example, but solely by the scope oi the appendedclaims.

What is claimed is:

1. In combination, controlling means comprising an inductive devicehaving a multipolar stator winding and a rotor winding in inductiverelation with said stator winding, a two-phase alternating currentdriving motor connected to actuate the rotor winding of said inductivedevice, a source of alternating current connected to energize one phaseof said driving motor, an induction device comprising a closed core ofhighly permeable magnetic material having a plurality of pole piecesprojecting therefrom adapted to receive a magnetic flux from auni-directional magnetic field, a winding on each of said pole pieces,said pole piece windings being connected in multipolar relation to themultipolar winding of said inductive device, a single phase winding onsaid closed core and energized by said source of alternating current forvarying the uni-directional flux in said pole pieces whereby anotheralternating current is induced in said pole piece windings, and meansconnecting the rotor winding of said inductive device to energize theother phase of said driving motor, whereby the latter rotates to actuatethe rotor of said inductive device upon relative angular movementbetween said induction device and said uni-directional magnetic field.

2. In combination, controlling means comprising an inductive devicehaving a multipolar stator winding and a rotor winding in inductiverelation with said stator winding, a two-phase alternating currentdriving motor connected to actaste the rotor winding of said inductivedevice, a source of alternating current connected to energize one phaseof said driving motor, direction responsive means comprising aninduction device including a, multipolar winding connected to themultipolar winding of said inductive device and a single phase windingenergized by said source of alternating current whereby anotheralternating current is generated in the multipolar winding of saidinduction device, and means connecting the rotor winding of saidinductive device to energize the other phase of said driving motor,whereby the latter rotates to actuate the rotor winding said inductivedevice upon relative angular displacement of said direction responsivemeans in azimuth.

3. An earth inductor compass comprising, in combination with anindicator, an electromagnetic device connected to said indicator andcomprising a rotor member and a stator member, one of said membershaving a multipolar winding, a two-phase driving motor drivablyconnected to the rotor member of said electromagnetic device, an earthinductor device comprising a closed core having three radiallyprojecting Dole pieces, a winding on each pole piece, said pole piecewindings being connected together in multipolar relation and eachwinding connected to a corresponding pole of the multipolar winding ofthe electromagnetic device, a winding on the closed core of said earthinductor devic and a source of alternating current connected to saidwinding of said inductor device and to one phas of said driving motor tosupply current to the winding of said one phase or said driving motorout of phase with the current supplied to the lastnamed winding of saidinductor device, the winding of the other phase of said driving motorbeing connected to the winding of the rotor of said electromagneticdevice, whereby displacement or the earth inductor device in azimuthproduces an electromotive force in the winding of the rotor member ofsaid electromagnetic device.

'4. In combination, controlling means comprising an inductive devicehaving a stator winding and a rotor winding, on of said windings beingpolyphase and the other being single phase, a two-phase alternatingcurrent driving motor connected to actuate the rotor winding of saidinductive device and having a winding in each phase, a source ofperiodically varying current connected to energize the winding of onephase of said driving motor, a magnetic induction device comprising arelatively stationary core of highly permeable magnetic material adaptedto be traversed by a magnetic flux from a uni-directional magnetic fieldand having a polyphase winding thereon, means connecting said induc tiondevice to said source of periodically varying current to vary thereluctance of said core whereby another periodically varying current isgenerated in the polyphase winding of said core member by the magneticflux traversing said core member, means connecting the polyphase windingof said induction device to the polyphase winding of said inductivedevice, and means connecting the single phase winding 01' said inductivedevice to energize the winding of the other phase of said driving motor,whereby the latter rotates to actuate the rotor winding of saidinductive device upon relative angular movement between the core of saidinduction device and said unidirectional magnetic field.

5. A magnetic compass comprising a magnetic pick-up device having astationary core of permeable material to be disposed in a unidirectionalmagnetic field, a multipolar winding on said pick-up device, an excitingwinding on said pick-up device, a source of periodically varying currentconnected to said exciting winding for periodically saturating saidpick-up device to produce in said multipolar winding an alternatingcurrent from said uni-directional field, a two-phase alternating currentdriving motor having a winding in each phase thereof, means connectingsaid source of periodically varying current to one phase winding of saidmotor for energization thereby, mean including amplifying meansconnecting the multipolar winding of said pick-up device to the otherphase winding of said motor whereby, upon relative angular displacementbetween said pickup device and said uni-directional field, said otherphase winding becomes energized by the alternating current produced fromsaid unidirectional field to cause said motor to rotate, and indicatingmeans controlled by the rotation of said motor.

6. In combination, controlling means comprising a magnetic pick-up ofpermeable material having a relatively stationary core and adapted to bedisposed in a uni-directional magnetic field for relative angulardisplacement with respect thereto, a multipolar winding on said pick-updevice, an exciting winding on said pickup device, a source ofperiodically varying current connected to said exciting winding forperiodically varying the reluctance of said pick-up device to produce insaid multipolar winding an alternating current from said uni-directionalmagnetic field, a two-phase alternating current driving motor having awinding in each phase thereof, means connecting said source ofperiodically varying current to one phase winding of said motor forenergization thereby, means including an amplifier connecting themultipolar winding of said pick-up device to the other phase winding ofsaid motor whereby, upon relative angular displacement between saidpick-up device and said uni-directional field, said other phase windingbecomes energized by the alternating current produced from saidunidirectional field to cause said motor to rotate, and means actuatedby said motor in accordance with the amount and direction of relativeangular displacement between said pick-up device and saiduni-directional field.

7. In an earth inductor compass, a gym-vertical, an earth inductiondevice comprising a relatively stationary core of permeable materialstabilized in a horizontal plane by said gyrovertical and disposed toreceive the horizontal component of the earths magnetic field, amultipolar winding on said core, an exciting winding on said core, asource of periodically varying current conected to said exciting windingfor periodically varying the magnetic reluctance of said core to producein said multipolar winding an alternating current from said horizontalcomponent of the earth's field, an inductive device having a rotorwinding and a stator winding in inductive relation with each other,indicating means connected to be actuated by said rotor winding, atwo-phase alternating current driving motor connected to actuate therotor winding of said inductive device, said motor having a winding ineach phase thereof, means connecting the multipolar winding of saidinduction device to one winding of said inductive device, meansconnecting said source of periodically varying current to one phasewinding of said motor, and means connecting the other winding of saidinductive device to the other phase winding of said motor whereby, uponrelative angular displacement of said induction device in azimuth withrespect to the earth's field, said other phase winding becomes energizedto cause said motor to rotate and actuate the motor winding of saidinductive device, thereby actuating said indicating means to indicatethe direction or the earth's field.

8. In combination, controlling means comprising an inductive devicehaving. a stator winding and a rotor winding, one of said windings beingpolyphase and the other being single phase, a two-phase alternatingcurrent driving motor connected to actuate the rotor windin of saidinductive device and having a winding in each phase, a source ofperiodically varying current connected to energize the winding of onephase of said driving motor, a magnetic induction device comprising arelatively stationary core of highly permeable magnetic material adaptedt be traversed by a magnetic flux from a uni-directional magnetic fieldand having a polyphase winding thereon, means connecting said inductiondevice to said source of periodically varying current to vary thereluctance of said core whereby another periodically varying current isgenerated in the polyphase winding of said core member by the magneticflux traversing said cor member, means connecting the polyphase windingof said induction device to the polyphase winding of said inductivedevice, means connecting the single phase winding of said inductivedevice to energize the winding of the other phase of said driving motor,whereby the latter rotates to actuate the rotor winding of saidinductive device upon relative angular movement between the core of saidinduction device and said uni-directional magnetic field, and agyrovertical having said induction device mounted thereon forstabilizing said device in the horizontal plane.

9. In combination, controlling means comprising a magnetic pick-updevice of permeable material having a relatively stationary core andadapted to be disposed in a uni-directional magnetic field for relativeangular displacement with respect thereto, a multipolar winding on saidpick-up device, an exciting winding on said pick-up device, a source ofperiodically varying current connected to said exciting winding forperiodically varying the reluctance of said pickup device to produce insaid multipolar winding an alternating current from said uni-directionalmagnetic field, a two-phase alternating current driving motor having awinding in each phase thereof, means connecting said source ofperiodically varying current to one phase winding of said motor forenergization thereby, means including an amplifier connecting themultipolar winding of said pick-up device to the other phase winding ofsaid motor whereby, upon relative angular displacement between saidpick-up device and said uni-directional field, said other phase windingbecomes energized by the alternating current produced from saiduni-directional field to cause said motor to rotate, means actutuated bysaid motor in accordance with the amount and direction of relativeangular displacement between said pick-up device and saiduni-directional field, and a gyro-vertical havin said magnetic pick-updevice mounted thereon for stabilizing said device in the horizontalplane.

10. In combination, controlling means comprising an inductive devicehaving a multipolar stator winding and a rotor winding in inductiverelation with said stator winding, a two-phase alternating currentdriving motor connected to actuate the rotor winding of said inductivedevice, a source of alternating current having a predeterminedfrequency, a frequency doubler connected to said source for doubling thefrequency of the current from said source, means connecting saidfrequency doubler to energize one phase of said driving motor by saiddouble frequency current, direction responsive means comprising aninduction device including a multipolar winding connected to themultipolar winding of said inductive device and a single phase windingenergized by said source of alternating current whereby anotheralternating current is generated in the multipolar winding of saidinduction device, having the same frequency as the double frequencycurrent from said frequency doubler, and means connecting the rotorwinding of said inductive device to energize the other phase of saiddriving motor, whereby the latter rotates to actuate the rotor windingof said inductive device upon relative angular displacement of saiddirection responsive means in azimuth.

11. In combination, controlling means comprising an inductive devicehaving a stator winding and a rotor winding, one of said windings beingpolyphase and the other being singlephase, a two-phase alternatingcurrent driving motor connected to actuate the rotor winding of saidinductive device and having a winding in each phase, a source ofperiodically varying current of predetermined frequency, means forproducing a second periodically varying current hav ing a frequencywhich is an even multiple of the frequency of said first current, meansconnecting one phase of said driving motor for energization by saidsecond current, a magnetic induction device adapted to be traversed by amagnetic flux of a uni-directional magnetic field and includingrelatively stationary core means of magnetically permeable materialhaving a polyphase winding and a single phase winding thereon, meansconnecting the polyphase winding of said induction device to thepolyphase winding of said inductive device, means connecting thesingle-phase winding of said induction device to said source ofperiodically varying current of predetermined frequency, whereby analternating current is generated in the polyphase winding of saidinduction device for energizing the polyphase winding of said inductivedevice, and means connecting the single phase winding of said inductivedevice to the other phase of said driving motor, whereby the latterrotates to actuate the rotor winding of said inductive device uponrelative angular movement between said induction device and saiduni-directional magnetic field.

12. In combination, controlling means comprising an inductive devicehaving a multipolar stator winding and a rotor winding in inductiverelation with said stator winding, a two-phase alternating currentdriving motor connected to actuate the rotor winding of said inductivedevice, a source of alternating current of predetermined frequency,means for producing a second alternating current having a frequencytwice that of said first alternating current, means connectingone phaseof said driving motor for energization by said second current, directionresponsive means comprising a magnetic induction device adapted to betraversed by a magnetic flux of a uni-directional magnetic field andincluding core means of magnetically permeable material having amulti-polar output winding and an input winding thereon, meansconnecting the muiti-polar winding of said induction device to themulti-polar winding of said inductive device, means connecting the inputwinding of said induction device to said source of alternating currentof predetermined frequency, whereby an alternating current is generatedin the multipolar output winding of said induction device having thesame frequency as said second alterhating current for energizing themulti-polar winding of said inductive device, and means connecting therotor winding of said inductive device to the other phase of saiddriving motor, whereby the latter rotates to actuate the rotor windingof said inductive device upon relative angular movement between saidinduction device and said uni-directional magnetic field.

ALFRED A. STUART, JR.

